JSFiddle - React, Tailwind, and code Playground

HTML

<pre id="output"></pre>

JavaScript

var arr = [
        { key: 'foo', val: 'bar' },
        { key: 'hello', val: 'world' }
    ];
    
    var result = arr.reduce(
        (accumulator, target) => ({ ...accumulator, [target.key]: target.val }),
        {});
    
    document.getElementById("output").innerHTML = JSON.stringify(result, undefined, 2);